With the introduction of single radio voice call continuity handover some services available over IP (Internet Protocol) networks (such as IMS (IP Multimedia Subsystem) voice service) can be continued over cellular circuit switched systems e.g. if the user moves to an area where the IP link cannot be maintained with a guaranteed quality of service. In this case, the session control needs to be seamlessly transferred from the IMS application (for example SIP (Session Initiation Protocol) based) to the circuit switched system call controller.